Art of pulverizing



Nov. 30 1926. 1,608,717

J. E. BELL ART OF PULVEHI Z ING Filed March 15 1923 6 Sheets-Sheet 1 INVENTOR (M B, Z:

17/77/555 i A TTORNE Y5 Nov. 30 1926.

' J. E. BELL ART OF PULVERiZING Filed March 15, 1923 6 Sheets-Sheet 2 &1 27

N V EN TOR I TTORNE Y5 Nov. 30 1926. 1,608,717

J. E. BELL ART OF PULVERIZING Filed March 15, 1923 6 Sheets-Sheet 3 VIII/I gm VENTOR a Y Z Z A TTORNE Y6 J. E. BELL ART OF PULVERIZING Nov. 30 1926.

Filed March 15, 1923 6 Sheets-Sheet 4 IN VEN TOR 5 M A TTORNEYJ (til v ll .llllll I 7/47? gi /1 -7% Nov. 30 1926.

J. E. BELL AH'I OF PULVERIZING Filed March 15,

1923 6 Sheets-Sheet 5 lil /IIIIII/III0YI;AZ JIIIJIIIIIJ,, W! I I W///// j wk.

IN VEN TOR A TTORNE Y5 Nov. 30 1926. 1,608,717

J. E. BELL ART OF PULVEBIZING Filed March 15, .1923 6 Sheets-Sheet 6 WIT/V15 S,

)% W/Ma/ ATTORNEYS Patented Nov. 30, 1926.

UNITED STATES JOHN I. BILL, 015' BROOKLYN,

, 1,608,717 PATENT OFFICE.

A CORPORATION 01' DELAWARE.

AB! PULVERIZING.

Application filed larch 15, 1828. Serial No. 825,188.

This invention relates to the art of pulverizing and it is especially useful in connection with the u verization of coal .to be burned under boilers, in metallurgical I furnaces and the like.

The apparatus is of the centrifugal type and depends upon the impingement of the coal on impact means with an impact velocity such that sufficient energy is developed to shatter or distintegrate the coal to the required fineness.

One of the primary objects of my invention is to provide a simple and effective apparatus of the character described in which the desired impact velocity is obtained, with a minimum expenditure of power well .within commercial limits, while at the same time the apparatus will free itself of the pulverized coal during operation.

I am aware that attempts have been heretofore made to pulverize by impact but such attempts have not realized the foregoing essentials. The so-called impact pulverizers now in use depend more upon striking the coal a succession of blows in a chamber or container than upon obtaining an initial velocity of impact sufficient to completely shatter the coal to the desired fineness and the process of pulverization 1s,

therefore, a slow one and the expenditure of power is relatively high. The amount of air passing through with the coal is also such that the requisite velocity cannot be obtained except at an expenditure of power so great as to be prohibitive.

I accomplish the foregoing, together with such other objects as may hereinafter appear, or are incident to my invention, by means of a construction and method, the preferred embodiments of which are illustrated in the accompanying drawings, wherein:

Fig. 1 is a side elevation of apparatus embodyingmy invention; Fig. 2 is a vertical section through the pulverizer of Fig. 1, drawn onan enlarged scale; Fig. 3 is a section taken on the line 3-3 of Fig. 2: Fig. 4 is a vertical section through another form of my invention; Fig. 5 is a plan view of a portion of the impeller casing of Fig. 4; Fig. 6 is a section taken on the line 6-6 of Fig. 5; Fig. 7 is a section through still another form of my invention; Fig. 8 is an end view of Fig. 7, drawn on a smaller scale; Figs. 9 and 10 are sectional views illustrating details of my shown) by means of the pipe 7 and the feeder mechanism consisting of the feeder casing 8, the feed screw 9, and the discharge throat 10 from the feeder casing. This throat may be restricted as shown, to limit the amount of air drawn through the apparatus.

The coal enters the throat 11 of a runner or impeller 12 which is mounted approximately centrally in the im eller casing 13, the impeller being rotate by means of the shaft 14 operated by a steam turbine B or other form of motor mechanism. The impeller is provided with impeller blades 15 and 16, the former being long and the latter short so as to prevent confusion or obstruction at the point where the coal first comes in contact therewith.

It will be observed that the impeller or runner is very similar to the runner employed in centrifugal pumps and that it is so formed that the coal enters the throat in a substantially vertically downward direction and is discharged from the periphery of the impeller in a substantially horizontal direction. coal first contacts with the blades, it has some rotary velocity due to having passed down through the revolving throat of the impeller, but the principal rotary velocities will be imparted after the coal enters the cavities defined by the blades. The number and disposition of. the blades is such that there is a uniform delivery of coal thereto and also a uniform discharge therefrom. Furthermore, the shape of the impeller is such that the shock incident to the passage of the coal from the throat 11 into the space between the blades is re duced to a minimum and the curvature of the passages is such that the direction of movement of the coal is changed with minimum resistance and obstruction and, therefore, with minimum wear. v

The line of flight of the particles from the periphery of the impeller will be somewhere between a tangent at right angles to At the point where the r the radius and an angle of more closely approximating the tangent than a 45 line.

In view of this, I have disposed about the periphery of the impeller a plurality of substantially equally spaced impact plates 16', the impact surfaces of which are very nearly at right angles to the line of flight of the coal articles discharging from the impeller an being inclined slightly away so that the pulverized coal after the impact, is carried away from the blades and into the peripheral collecting or receiving chamber 17 formed in the casing 13. Theoretically, perhaps, the impact surfaces should not be lanes, but one of the most diflicult probems to overcome in apparatus of this character is the freeing of the coal after pulverization, to which end I have not only provided the arrangement of impact blades shown but also the disposition of the collecting or receiving chamber beyond the impact blades. The number an spacing of the im act blades is such, in relation to the impel er, that a substantially uniform discharge of pulverized material takes place into the receiving chamber.

The pulverized coal is carried by air, as will further appear, from the receiving chamber to a classifier or separator C by means of a plurality of pipes 18, preferably four in number. This classifier is of a cyclone type well understood in this art and the fine material is carried from the classifier in suspension to-a cyclone separator D through the pipes 19, the particles not shattered to suificient fineness falling to the bottom of the classifier and being discharged into the casing 8 of the feeder mechanism through the medium of. feed means. gener ally indicated at 20 and operated, as will further appear.

In the cyclone separator D, final separation of the coal from the air is brought about and the air is returned by the pipe 20 to the feed pipe 7 and also, by virtue of the branch 21, to the throat 10.

A circulation is set up through the system by virtue of the fact that the impeller acts as a suction fan at high speeds. The volume of air to be handled in addition to the coal largely determines the expenditure ofpower required to rotate the impeller. I prefer to rotate the impeller at a top speed of about 25,000 to 30,000 ft. per minute, and it will at once be seen that if the volume of air to be handled at this speed through the impeller is large, the expenditure of power will be prohibitive. To overcome this difliculty I control the amount of air in the system, as for example, by always maintaining a sufii cient bed of coal in the bin feeding the pipe 7 to act substantially as a seal, a relief 22 being provided in case there should be too much leakage into the system. The

area of the feeder casing is small so that leakage is still further restricted. To .prevent pulverized material from lodging between the impeller and the casin on the up r side of the im ller, shoufii any partic fly in that direction, I provide anannular rib 23, and to prevent suction of descending coal particles out between the throatll and the throat 10, I provide the packing 24 and also cause the lip 10' of the throat 10 to pro'ect' somewhat into the throat 11. Shoul any material work its way into the space beneath the impeller which is a remote possibility, the same will be dra ged out by the suction. The packing 24 "revents leaks into the casin The riving mechanism will I10W36 described. The shaft 14 has a thread 25 which drives a worm 26 keyed to the shaft 27. Through the medium of the-belt 28 the shaft 27 drives a shaft 29 which, in turn, through the medium of a cone pulle mechanism 30, drives the shaft 9 and t e screw 9. The cone pulley drive affords a means for regulating the speed of the feed screw with reference to the speed of the main shaft. The supply of steam to the turbine is controlled by means of the 'governor mechanism 31 operated by the belt 32 from the shaft 27. By this arran ment the turbine is caused to run uni ormly and the speed of the feed screw 9 may be ad'usted in accordance withthe speed of revo ution of the main shaft. This is importantto efficient and successful operation, particularly since the speed of the im ller will vary as indicated, developing an impact velocity of from about 400 ft. per second to about 500 ft. per second. The'feeder 20' is operated by the shaft 9' through the gearing 33.

With regard to the amount'of air passing through the system with the coal, I prefer to use, as nearly as possible, the amount of air necessary to pass the coal through the apparatus to the classifier. I prefer, in the arrangement of Figs. 1 and 2, to use from lb. to about 1 1b. of air per pound of coal which is much less than the quantity here- It will be seen from the foregoing that A theoretically considered, each particle of coal is shattered to the required fineness by a single impact blow, the pulverized material being immediately freed of the machine so that difiiculties in connection with choking are avoided; in contradistinction to apparatus in which the coal particles are subjected to successive impact or blows, as described, or treated in a chamber in which unshattered and shattered coal are in indiscriminate relative motion and confusion. Should there be any material which isnot sufliciently finely pulverized, such material does not remain in-the pulverizer portion, proper, of the apparatus but is passed out along with the more finely pulverized material and then separated therefrom and again cycled through the machine.

The impact blades 16' are adjustable as to angularity, as will be clear from inspection of Figs. 9 and 10. The relative restriction of that section of the casing in which the impact blades are located ensures a relatively high velocity of the air passing outwardly therethrough so that this, in connection with the velocity and direction of the discharging fuel particles, further ensures that the pulverized material will pass to the collecting chamber. r y

In the arrangement of Figs. 4 and 11, which in some respects is preferred, a separate system of conveying air is provided. In this arrangement a very small quantity of air is rovided for the incoming coal by maintaining a layer of coal in the bin of sufficient depth to substantially act as a seal and by the restrictions of the feeding mechanism through which but a relatively small leakage can take place, the major portion of the air being supplied by the variable speed fan F to which the return pipe 20' leads and from which there is a connection to the inlet 34 in the upper portion of the receiving chamber 17. The discharge outlet 35 opens from the bottom of such receiving chamber at a point approximately below the inlet 34 and a single pipe 18 leads from such outlet to the classifier, as before.

The air entering the inlet 34 passes around the collecting chamber 17, as indicated by the arrow, escaping through the outlet 35. The direction of inlet and outlet of the air is such as to produce a whirling or ,vortical motion to the air passing around the collecting chamber so as to ensure the picking up of the pulverized material discharged into the lower portion thereof, the energy for producing and maintai..ing this motion and for picking up the pulverized material is obtained through the lower pressure or greater suction obtaining in the outlet 35 than is carried in the inlet 34. Pressure conditions throughout the casing are thus maintained substantially uniform and the pulverized material is ensured of being carried along in suspension and by entrainment so that no collection or deposit thereof takes place, and so that a uniform discharge from the impact plates around the casing is had. This object is served to some extent also by making the receiving chamber of considerable depth, as shown.

In Figs. 7 and 8 the apparatus is shown as being horizontall disposed, the only substantial departure being that the air inlet 34 and the discharge outlet 35 from the receiving chamber, are located at the bottom, in alignment. The discharge from the impeller-is also substantially central of the collecting chamber. In this arrangement the air discharged from the periphery of the impeller will cause the pulverized material to work around to the bottom in position to be entrained by the current of air passing throu h the separating system. At the high speeds, gravity has no eifect and there will be a uniform peripheral discharge.

What I claim is:

1. In a centrifugal pulverizer, the combination of a rotary impeller, and spaced impact members against which the impeller delivers the material and through the spacer between which the pulverized material passes freely outwardly, together with means U for adjustment of the impact members.

2. A pulverizer comprising concentrically serially arranged impeller, impact means and receiver whereof the impeller is adapted to impel the material against the impact surfaces so that it is pulverizedin passing outwardly to the receiver, said pulverizer being closed against air admission save through a regulable supply, and means for regulably supplying air to the pulverizer.

3. The herein described process of pulverizing material which consists in passing the material through a centrifugal pulverizer with a weight of air approximately from one half of to not materially more than the weight of the coal.

In testimony whereof, I have hereunto signed my name.

JOHN E. BELL. 

